Ultraviolet light detectors have become of increasing importance with the development of short pulse lasers producing electromagnetic radiation in the ultraviolet or near ultraviolet wavelength region of the electromagnetic spectrum.
Crystalline silicon ultraviolet detectors are known. Those detectors typically include an intrinsic, i.e., effectively undoped, region sandwiched between oppositely doped, i.e., one p-type and one n-type, layers. The light to be detected enters through one of the doped regions and some of the unabsorbed light that reaches the intrinsic region produces charge carriers that are collected as an indication of the presence of ultraviolet light. The response and efficiency of these crystalline detectors is limited by the quantity of light absorbed in the "front" doped region through which the light must pass in order to reach the intrinsic region. In order to achieve the doping level necessary for good performance, that "front" doped region must have a thickness of several hundred nanometers (nm). But the strong absorption of ultraviolet light in a crystalline front region of that thickness limits the quantum efficiency of crystalline silicon detectors. In addition, crystalline silicon detectors show some instability after exposure to ultraviolet light.
To overcome the quantum efficiency limitations in crystalline silicon ultraviolet light detectors, materials other than silicon are employed in some ultraviolet detectors. For example, Schottky barrier ultraviolet light detectors employing gallium arsenide phosphide are commercially available. However, these alternative material photovoltaic detectors of ultraviolet light are expensive because of the materials employed.
Other ultraviolet light detectors are also known. A summary of the state of the art appears in two articles by Wilson and Lyall published in 24 Applied Optics 4530-4546 (December 1986). None of the available detectors achieves low cost, long term stability and high efficiency.
Accordingly, it would be useful to provide a low cost, high efficiency, solid state photovoltaic detector of ultraviolet radiation that is stable over time.